The conventional process for making capacitive switching devices, such as the switching devices of the keyboards described in U.S. Pat. Nos. 3,968,336 and 3,969,595, includes the steps of providing on a layer of conductive material a photoresist having a desired spring pattern configuration, removing by acid treatment the portions of the layer of conductive material not protected by the photoresist, removing the photoresist to provide one or more discrete electrode areas, and applying an insulating (dielectric) curable adhesive layer to each of the discrete electrode areas. The insulating (dielectric) layer, which limits the magnitude of the capacitive reactance when the switching mechanism is fully depressed, is applied by a spraying process, such as by aerosol spraying of a solvent-based lacquer which dries to a smooth insulating layer.
Due to its method of deposition, the dielectric suffers from non-uniformity of thickness between different electrode areas, as well as non-uniformity over each individual electrode area. Furthermore, the dielectric is subject to pinhole formation. Another disadvantage of a dielectric deposited as described is that the increased handling of the conductive layer having the discrete electrode areas strongly increases the likelihood of damage to the fragile electrode areas.